<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>websocket</title>
</head>
<body>
<script>
   let socket = new WebSocket('ws://localhost:9999');  
   //当连接成功之后就会执行回调函数
   socket.onopen = function(){
       console.log('客户端连接成功');
       //再向服务 器发送一个消息
       socket.send('hello');//客户端发的消息内容 为hello
   }   
   //绑定事件是用加属性的方式
   socket.onmessage = function(event){
       console.log('收到服务器端的响应',event.data);
   }
</script>
</body>
</html>